1. Field of Invention
The present invention relates to towers, shafts and stairways. More particularly, the present invention relates to precast stackable concrete bodies, each precast body having four structurally interconnected walls defining a medial channel extending therethrough, the precast bodies are stackable vertically to provide a tower and/or shaft having a continuous medial channel extending therethrough and a continuous flight of stairs extending through the medial channel of the tower and/or shaft.
2. Background
Many construction projects including, but not limited, to mining, pumping stations, cooling towers, underwater construction, underground geothermal installations, and above ground access chambers whether of new construction or retro-fit/remodeling have a need for vertical shafts for elevators, stairs and/or service equipment such as communication, plumbing and electrical. Regulations and building codes for such shaft structures are replete with requirements for safety, access, and ingress and egress redundancy.
It is known in the construction industry for shafts and towers to be either “cast in place” or formed using “precast planar wall panels” that are attached to one another “in-situ” to form the shaft.
Generally, towers and shafts for elevators, stairs, service equipment, and the like are formed by establishing a supporting foundation at the lowest level, and then constructing the shaft/tower vertically upwardly from the foundation which may be at ground level, below ground level or above ground level. For purposes of this disclosure, the method is described for constructing a shaft below grade (i.e. below ground level) but the process for constructing a tower (above grade) is similar except that the components are hoisted vertically upwardly to be placed upon an uppermost level as opposed to lowered into a shaft to connect with a previously positioned level.
When the “cast in place” method is used, a shaft is excavated in the ground and movable, spaced apart forms are positioned to form an inside surface of a shaft/tower wall and at a position to form an outside/exterior surface of the shaft/tower wall. Reinforcing elements such as steel, and/or rebar may be added to the space between the two forms and concrete is then poured into the space defined between the forms and about the reinforcing elements. As the concrete at the lowest levels cures/hardens, the forms are moved and repositioned upwardly and more reinforcing is added and more concrete is poured. The process is repeated/continued until the desired uppermost level is formed. This “cast in place” method is complex, dangerous and time consuming, especially when a below grade shaft is being formed because a shaft requires workers to be within the shaft to position and move the forms, install the reinforcing, pour the concrete, and all of the construction materials must be lowered down the shaft from above while the workers are within the shaft. After the shaft/tower is complete, stairs may be added to interior shaft walls by attaching fastening means to the interior shaft walls and thereafter attaching stringers/flights of stairs to the fastening means after lowering the stringers/flights of stairs down the shaft from above.
When the pre-cast planar wall panel method/process is used to construct a below grade shaft, the pre-cast planar wall panels are hoisted with a crane and lowered into the shaft and positioned one at a time upon a foundation and fastened thereto. Thereafter, additional pre-cast planar wall panels are fastened to the previously installed pre-cast wall panels along adjacent edge portions. This method is also complex, dangerous and time consuming because it requires workers to be within the shaft to position and align the pre-cast planar wall panels, to support the pre-cast wall panels while the level is completed, to interconnect the panels together, to caulk or otherwise seal the joints between the adjacent panels and all of the construction materials must be lowered down the shaft from above while the workers are within the shaft. Each of the pre-cast planar wall panels generally carries at least one weld-plate at each end portion and at top and bottom portions that are positioned immediately adjacent similar weld-plates carried by immediately adjacent pre-cast wall panels when the wall panel is properly positioned. The weld-plates are “welded” together to provide additional strength and integrity between the adjacent wall panels. Unfortunately the welding of weld plates may require workers to access both the interior and exterior portions of the pre-cast planar panels within the shaft. The weld plates also add complexity to the pre-casting of the planar wall panels as the weld plates must be correctly positioned within the forms prior to the concrete being poured into the forms, and the “bonding” of metal to concrete can be problematic as such interfaces are subject to corrosion, chemical reactions and the like that can, over time, weaken the concrete proximate to the metal weld plate and/or weaken the metal comprising the weld plate and/or weaken the weld interconnecting the adjacent weld plates.
Such known methods for forming towers and shafts are complex, dangerous to workers, expensive and time consuming. In the situations where a shaft is being constructed below grade, “shoring” and support must be installed and maintained throughout the length of the shaft for the duration of the project to prevent collapse of the surrounding earth defining the shaft. There may also be a need for a temporary elevator or lift for workers to reach the work site inside the shaft such as to move the forms and weld the weld-plates to one another. After the shaft is complete, workers must seal/caulk the joints between the adjacent panels and install flights of stairs within the shaft by attaching fasteners to inside walls of the shaft at specified locations, and thereafter attaching stringers of stairs to the fasteners which are lowered down the shaft from above. This work is hazardous as the flights of stairs must be lowered down the shaft from above while the workers are within the shaft. Further yet, when the shaft to be constructed is below grade level, the “hole” in which the shaft is constructed needs to be significantly larger than the ultimate finished shaft size because of the need for workers to readily and safely access the exterior of the forms while the shaft wall is being built.
The instant invention overcomes various of the aforementioned drawbacks to known construction methods and apparatus for towers and shafts by providing a precast stackable peripherally defined unit having four structurally interconnected spaced apart tower/shaft walls defining a medial channel extending therethrough. Each stackable unit may carry a preinstalled flight of stairs within the channel defined by the walls. A locking protrusion and a locking recess defined in diametrically and vertically opposing top and bottom corners of each unit allows units to be stacked on top of one another providing a continuing staircase within the medial channel. Because each unit is integral, having four interconnected cooperating supporting walls the thickness of the walls may be reduced while maintaining necessary strength and rigidity and reducing weight. Further, because the four walls are formed as a single unit there are no vertical seams that need to be caulked or otherwise sealed because as each unit is stacked in place that level is complete and useable by workers. Because each unit is similar, the concrete forms for casting the units are all the same. Horizontal seams between immediately adjacent units carry a pre-installed pliable sealant such as, but not limited to butyl tape which provides a fluid tight seal between immediately adjacent units. Weight of the stacked units compresses the pliable sealant which may be applied to an upper and/or lower surface edge of each unit prior to installation further reducing labor costs and time.
Further still, because there is only a limited need for workers to physically access and work on the exterior surface portions of the units during installation, the shaft may be smaller further reducing time and associated costs. Because the flights of stairs may be preinstalled within the units as the units are stacked upon one another the stairway is also simultaneously constructed, eliminating the need for subsequent stair installation which even further reduces costs and installation time.
Some or all of the problems, difficulties and drawbacks identified above and other problems, difficulties, and drawbacks may be helped or solved by the inventions shown and described herein. The instant invention may also be used to address other problems, difficulties, and drawbacks not set out above or which are only understood or appreciated at a later time. The future may also bring to light currently unknown or unrecognized benefits which may be appreciated, or more fully appreciated, in the future associated with the novel inventions shown and described herein.